2,2′,6,6′-tetraisopropyl-4,4′-biphenol (hereinafter referred to as biphenol) is an anti-epileptic compound newly developed (Chinese patent CN 101804043A, Uses of biphenol and its derivatives in drugs for the treatment of epilepsy) for treating many epileptic symptoms such as generalized tonic-clonic seizures (grand mal), absence seizures (petit mal), simple partial seizures, complex partial seizures (psychomotor seizures), autonomic seizures (periodic seizures) and others. Experimental studies have shown that biphenol has a strong affinity towards GABA receptors and is a GABA agonist, while it is an antagonist for NMDA receptors for regulating the Ca2+ influx in Ca2+ channels. Biphenol also offers protection against the excitotoxic effect induced by kainate (kainic acid). Studies have confirmed that biphenol is a significantly stronger antioxidant than propofol and has a stronger protective effect on the brain. Of particular importance is that biphenol does not cause the patients to lose consciousness and therefore has important clinical values in the treatment of patients with different types of epilepsy.
However, biphenol is a highly lipid soluble compound that is difficult to dissolve in water. Studies have shown that it is difficult to achieve a desired effect by using surfactants such as cyclodextrin, Tween 80, Vc or DMSO to assist or increase its dissolution and, thereby, its efficacy is affected and its clinical application becomes limited. In this invention, lipid microspheres are used as a drug carrier for the biphenol. This not only overcomes the problems due to insolubility of biphenol, but also allows the drug to be selectively accumulated in a lesion site and maximizes the amount of drug that is delivered to a targeted site so that the concentration of the drug at that site can be increased by several to hundred times above that of conventional preparations to improve its therapeutic effect. At the same time, there is minimal amount of drugs distributed in healthy tissues such that any cytotoxic side effects and adverse reactions are significantly reduced, and hence high efficacy with low toxicity would be achieved. Currently, there has been no report on biphenol lipid microsphere preparations. Therefore, the rational formulation of a preparation based on the physiochemical properties of biphenol for safe, stable and effective biphenol lipid microspheres is an issue this invention will address.
The present invention provides a 2,2′,6,6′-tetraisopropyl-4,4′-biphenol lipid microsphere preparation and its preparation method. 0.5˜1% of antioxidants were added to the preparation to address the issue that biphenol is easily oxidizable. Particularly, vitamin E, a potent, lipid soluble antioxidant, is used for ensuring the stability of the drug in the preparation. This invention uses only phospholipid emulsifiers in an amount of 1 to 1.5% without any co-solvent so as to prevent hemolysis and production of substances that may otherwise cause thrombotic inflammation. Further, the emulsifiers of this invention are egg lecithin derived from the yolk of animal embryos which are easier and safer to be absorbed by the human body.